The decision comes over a month after the United States Senate failed to pass the Pain-Capable Unborn Child Protection Act, which would have banned abortion after 20 weeks. Senator Durbin was among 14 Catholics who voted against the Act.

In a statement issued by the diocese, Bishop Paprocki concurred with Cardinal Timothy Dolan, Chairman of the United States Conference of Catholic Bishops’ Committee on Pro-Life Activities, who called its failure “appalling”.

The bishop cited Canon 915: those “who obstinately persist in manifest grave sin are not to be admitted to Holy Communion.”

He then quoted the USCCB’s 2004 Statement on Catholics in Political Life: “Failing to protect the lives of innocent and defenceless members of the human race is to sin against justice,” it reads. “Those who formulate law therefore have an obligation in conscience to work toward correcting morally defective laws, lest they be guilty of cooperating in evil and in sinning against the common good.”

Bishop Paprocki said Durbin’s pro-abortion voting record proves “obstinate persistence in manifest grave sin.” Therefore, “the determination continues that Sen Durbin is not to be admitted to Holy Communion until he repents of this sin.”

“This provision is intended not to punish, but to bring about a change of heart,” he assures readers. “Sen Durbin was once pro-life. I sincerely pray that he will repent and return to being pro-life.”

The bishop appears to pre-empt common objections to the practice of denying the Sacrament to politicians who support abortion. In 2009 Cardinal Donald Wuerl, the Archbishop of Washington, expressed concern over “Communion wielded as a weapon”. “That’s the new way now to make your point,” he added.

Other American prelates have long defended the practice. When John Kerry visited Missouri during the 2004 presidential election, Cardinal Raymond Burke – then Archbishop of St Louis – denied him access to the Eucharist.